Yep, you can generally fit a 26x1.25 tire on standard mountain bike rims, and that is a good size for a commuter. Look for a tire with minimal to moderate tread (no lugs), and ideally Kevlar belted for puncture resistance.
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Daniel R HicksApr 30 '12 at 21:51

In my opinion it's a fallacy to believe that a city bike should have thin tires and in fact if you look at bikes that are specifically marketed as city bikes (and don't aim at the hipster single speed crowd) they often come with quite wide tires.

Wide tires offer much more dampening and the difference in rolling resistance is much smaller than once believed. Since city roads and bike lanes often aren't very smooth this means a considerable plus in comfort at virtually no cost.

For me slightly modified MTBs make perfect city/allround bikes and as far as tires go I personally love Continental Town & Country.

I agree, for commuting a good tire size would be 40-45mm. With tires of that width, you don't have to care what kind of cracks/curbs/bumps you roll over, and it's much less jarring on the hands and wrists. On my hardtail mountain bike, when I'm not riding singletrack trails, I use Continental Touring Plus 47mm tires. They are a bit heavy, but they don't slow me down much, even on 100+ mile rides. Never had to worry about punctures or pinch flats, either.
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NikApr 10 at 20:19

That said, it is worthwhile to have a set of slick tires for commuting.
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NikApr 10 at 20:20